JPH0799461B2 - Driving method of display device and driving output inverter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a driving method and a driving circuit for a thin display, which has been rapidly increasing in importance in recent years. More specifically, the present invention relates to a new drive method and a drive output inverter for realizing a large display capacity and low power consumption of an XY dot matrix type AC-refresh plasma display device.

[Conventional technology]

A plasma display is a display device that utilizes the discharge phenomenon of a rare gas, and the development and commercialization of a large-capacity display device is competing with the recent strong need for thin, lightweight office and industrial displays. Plasma display (PD
P) is roughly classified into a DC type that uses a DC discharge and an AC type that applies an AC voltage. Of the AC type, the type that stores facial expression information as wall charges inside the panel and displays this is called the memory type, and the one that repeatedly reads and displays the information stored in the external memory is called the refresh type.
Each has its own characteristics.

The AC-refresh type PDP targeted by the present invention has the advantages that the panel structure is simple, the visibility is good, the reliability and the life are excellent. The emission brightness of the AC-refresh type PDP is determined by the number of times the discharge cell emits light, that is, the number of AC pulse voltages applied to the cell. When the refresh type XY dot matrix display panel is configured, the drive circuit is a line sequential scanning system as shown in FIG. By the scanning circuit 21, one scanning electrode (row electrode y ₁
... y _n ) is selected and the required high voltage pulse train is applied for the selected period. At the same time, the column electrodes (x ₁ …
A high-voltage pulse train of opposite phase is input from the (x _m ) side according to the data signal from the image data signal input circuit 22 corresponding to the selected electrode, and the cell at the intersection of both electrodes emits light in proportion to the number of applied pulses. To do. By the way, in large display capacity PDP,
At least 400 scanning electrodes are required. In order to obtain sufficient display brightness with such a large PDP, it is necessary to increase the panel drive frequency according to the number of scan electrodes.
In fact, if it is necessary to apply an AC pulse of 2000 times / sec to the display cell in order to obtain sufficient display brightness, the driving frequency required for a panel having 400 scanning electrodes is 2000 × 400 = 800.
It becomes [kHz]. The voltage required for gas discharge is usually 120-150V
Since it is (one side), high frequency and high voltage are required to drive a large capacity AC-PDP.
Reducing power consumption was a major issue.

In contrast, the 1984 SID (Society for Information Dis
play) Technical Digest "An
AC Refresh PDP with High ・ Voltige CMOS Drivers an
In "d Unbalanced Power Supplies" (lecture number 7.5, P.99), the "high-speed high-voltage CMOS drive circuit" that replaces the conventional high-voltage bipolar drive circuit, and the scan-side drive voltage that is as high as possible for low power consumption, An "unbalanced drive method" has been proposed in which the drive voltage on the data side is made as low as possible.By these methods, a large capacity PDP (for example, 400 scan electrodes x 640) that consumes about an order of magnitude lower than the conventional method is used.
Data electrode panel) has been realized.

[Problems to be solved by the invention]

By the way, due to the rapid progress of information society in recent years, there is an increasing need for a display device that consumes less power so that it can be used with a battery and a display device that has a larger capacity. In order to drive the battery, it is necessary to operate at several W at most. on the other hand,
In order to increase the capacity, it is required to realize a large capacity display panel having multiple scanning electrodes such as 1000 and 2000 lines.
For example, if the number of electrodes of a 400 × 640 dot display panel is doubled to 800 × 1280 dots, the number of display dots is quadrupled. The high-speed CMOS drive circuit enables more than 4 times the power consumption of the panel due to the increase in drive frequency and load capacity even though scanning is sufficiently possible. On the scan electrode side driven for each row, the number of electrodes is doubled and the load capacitance of each electrode is doubled. Therefore, the load on the drive circuit is quadrupled in total. On the data electrode side, however, the frequency is doubled, the number of electrodes is doubled, the load capacity of each electrode is doubled, and the total load on the drive circuit is increased by eight times. Originally, in AC-refresh PDP, the driving power on the data side, which is driven simultaneously, is much larger than that on the scanning side.
When the display capacity is expanded four times as in the previous example, the increase in power consumption of the entire PDP is not four times but rather nearly eight times.

The object of the present invention is to significantly reduce the driving power consumption on the data electrode side by a new data electrode driving method and driving circuit based on the principle of plasma gas discharge, and thus to realize a PDP with low power consumption and large display capacity. It is what

[Means for solving problems]

To achieve the above object, the present invention applies a high-voltage pulse train from the scan electrode side and a low-voltage pulse train of opposite phase from the data electrode side, and selectively emits line-sequential intersections thereof to display information. In a method of driving an XY dot matrix type AC-refresh plasma display device, a total voltage value of a scan electrode side pulse and a data electrode side pulse is set to be sufficiently larger than a gas discharge starting voltage in the initial stage of voltage pulse train application. At least one data electrode side pulse having a large magnitude is applied, and then the data electrode side pulse voltage is lowered to a level at which the total voltage value can secure the gas discharge holding voltage.

In order to achieve the above object, the present invention applies a high-voltage pulse train from the scan electrode side and a low-voltage pulse train having an opposite phase from the data electrode side, and selectively emits line-sequential light at the intersections thereof to obtain information. XY dot matrix type AC for display
A drive output inverter of a refresh plasma display device, comprising one drive MOS transistor and at least two load MOS transistors having different conductivity types from the MOS transistors, each load MOS transistor being Load MOSs other than load MOS transistors connected to power supplies of different potentials and independent gate input means and at least connected to the highest potential power supply
A diode element is inserted between the transistor and the output terminal so that at least two or more different voltage pulses can be output.

[Principle / Action]

A detailed study of the relationship between the drive voltage pulse of the AC-refresh PDP and the discharge light emission phenomenon revealed the following facts. That is, the improved PD described in the above-mentioned document.
In the P drive method, a high voltage pulse is applied from the scan side to the limit that does not cause a malfunction due to one side drive, and the voltage amount necessary for starting discharge is applied from the data side.

In the selected light emitting cell, both applied voltages having opposite phases are superimposed on each other, and discharge light emission occurs if the sum exceeds the discharge start voltage. In the large display capacity PDP that was the subject of the study, about 170 V was the maximum allowable drive voltage on the scanning side, and about 45 V was the minimum allowable voltage on the data side, including a margin. On the other hand, when the voltage on the data side was gradually decreased during one-time lighting and still display, discharge light emission was not interrupted even when the allowable minimum voltage of 45V was exceeded. When the voltage on the data side was gradually lowered, any of the discharging display cells continued to emit light at least up to around 30 V, and the light emission was partially stopped below that. This is because once the discharge is started,
It is considered that so-called wall charges grow in the discharge cells, which affects until the next refresh driving, and the voltage required for starting the next discharge is lowered. Therefore, in the present invention, when a drive voltage pulse train is applied to a discharge cell for a selected period, a high data-side voltage pulse that is high enough to start a new discharge is applied at the initial stage, and then the data-side voltage pulse is applied. It was decided to reduce the pulse. By doing so, if any discharge cell is selected, light emission is surely started. On the other hand, for example,
By applying a lower data-side voltage pulse during 90% or more of the selection period, the data-side driving power can be reduced substantially in proportion to the square of the data-side power supply voltage.
Since the drive power on the data side accounts for a very large proportion of the power consumption of the device, if this drive method is adopted, the power consumption of the entire display device can be greatly reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 (a) shows the waveforms of the high voltage pulse inputs on the scanning side and the data side in one embodiment for carrying out the driving method of the present invention. The PDP to which the present invention is applied may be basically the one described in the above-mentioned paper except that the driving voltage pulse is changed. In this embodiment, a scan side pulse SP of 1 MHz, V _SC = 170 V is applied to the selected scan electrode. on the other hand,
A relatively high starting pulse V _H1 (for example, 60 V) for starting discharge is input as the data-side pulse DP. In the figure of this embodiment, three starting pulses are drawn. The number of starting pulses depends on the characteristics of the panel itself and the applied voltage value,
Specifically, one to several are suitable. In short, what is required for this start-up pulse is the voltage value and pulse width required to start the discharge, and the number of repetitions required to create the wall charge required for the discharge to continue constantly. . Now, next, the voltage on the data side is lowered to V _H2 (= 15V). After that, during one scanning period, V _SC = 1 in the selective discharge cell.
70 V, V _H2 = 15 V, and a drive pulse with a repetition frequency of 1 MHz is input to emit light. In this way, when the electrode scanning for one screen is completed, the same selective scanning is repeated in sequence,
Display information.

In the embodiment of the present invention, the data side voltage for continuous discharge is set to 15
I was able to drastically reduce it to the V level. This is because the discharge is surely started by the high voltage pulse at the start of each scan (60 to 70 times / sec), and the wall charge that needs to be continuously discharged is formed at each low voltage. By the way, when the sum of the AC drive pulse voltages (V _SC + V _H2 ) is made small, the emission brightness is slightly lowered, but it is possible to easily compensate by slightly raising the drive frequency. After all, the drive voltage on the data side could be reduced from the conventional 45V to 15V by adopting this method, so (15/45) ² = 1/9, the power consumption during continuous discharge is only one ninth. became. Even if the power for the start-up pulse and the high-frequency power for maintaining the brightness were taken into account, the power consumption on the data side was reduced from one quarter to one fifth. Therefore, according to the driving method of the present invention, even if a large-capacity PDP having a vertical and horizontal doubling and a display area quadruple is configured, the total power consumption increases only to about twice that of the conventional panel.

FIG. 2 is a drive voltage pulse waveform diagram showing a second embodiment of the drive method of the present invention. In this embodiment, the repetition frequency of the starting pulse is set relatively slow (for example, 500 kHz), and the driving frequency during the scanning period for obtaining the brightness thereafter is set high (1 MHz or more). When the starting pulse width is wide, sufficient wall charges grow during that period, so that the starting voltage value can be lowered. For example, in this embodiment, V _{H1 is set} to 3
Even at 5-40V, sufficient discharge start was secured. According to such so-called frequency modulation driving, it is advantageous that a uniform discharge starting voltage can be set over the entire surface of the large display area panel even with a low data side voltage.

FIG. 1B shows an example of a drive output inverter circuit that realizes these embodiments. In this circuit example, one drive MOS transistor is connected to a power supply of a higher voltage (V _H1 ) having a conductivity type different from that of the drive MOS transistor and a load MOS transistor 1 and a power supply of a low voltage (V _H2 ). The load transistor 2 is provided, and the load MOS transistor 2 and the diode 4 are provided between the output terminals 3. Each MOS transistor has an independent gate input,
It can be turned on and off at independent timings. The start pulse of V _H1 is the load MOS transistor 1 and the drive MOS.
It is output by operating the transistor 5 as a set of inverters. At this time, the circuit on the V _H2 side is separated by the diode 4. Next, the load MOS transistor 1 is turned off, and the load MOS transistor 2 and the drive MOS are
A V _H2 pulse is output in combination with the transistor 5. As shown, these circuits are
Since it has a CMOS configuration due to the combination of OS and NMOS transistors, high speed and low power consumption characteristics can be obtained. By using this circuit, it is possible to easily solve the problem of outputting high-voltage pulses and low-voltage pulses at high speed from a small-scale circuit, which was difficult to realize in the past. Further, if the load MOS transistors are multi-staged and each of them is provided with a diode as shown in FIG. 1 (b), it is possible to obtain pulse output of two or more kinds of voltage values with one CMOS configuration inverter.

FIGS. 3 and 4 are diagrams showing a configuration example in the case where a display panel drive circuit is configured by using the drive CMOS configuration output inverter. FIG. 3 shows a case where the CMOS configuration inverter 11 is used as a pulse source for driving the entire data side. The pulse voltage output from the CMOS configuration inverter 11 is selected by the switch circuit 12. It is sent to the data electrode of the display panel 13. In this case, one or several CMOS configuration inverter circuits having a sufficient current supply capability may be provided. Reference numeral 14 is a control circuit, and 15 is a scanning circuit. FIG. 4 shows a circuit system in which the above-mentioned CMOS inverters 11 are prepared for the number of electrodes on the data side of the display panel without using a switch circuit. Finally, the data side circuit is
It is desirable to realize it with a large-scale IC including the OS inverter output stage.

Both the first and second embodiments can be realized by using the drive circuit configurations shown in FIGS. 3 and 4 and only adjusting the drive timing by the control circuit or the like.

〔The invention's effect〕

According to the driving method of the present invention, it is possible to uniformly and evenly start and continue the discharge of the dot matrix PDP at a low voltage, and it is possible to greatly reduce the power consumption on the data side. Further, according to the driving CMOS configuration output inverter of the present invention, it is possible to solve at once a problem that was difficult to realize in the past in which different high frequency / high voltage pulses are output from a small-scale / low-cost circuit. The circuit can be easily integrated on a large scale and has an extremely great industrial value.

Further, according to the embodiment of the present invention, the total power consumption required for driving the PDP is reduced to several watts, which is about 1/3 of the conventional power consumption. This means that the PDP can be used as a battery-powered portable display terminal, and the field of use of the PDP will be greatly expanded. On the other hand, even if a large display capacity PDP having an area four times as large as that of the conventional panel is constructed, the power consumption can be reduced to at most about twice by adopting the driving method of the present invention. The invention greatly contributes greatly.

[Brief description of drawings]

FIG. 1 (a) is a drive pulse waveform diagram in the embodiment of the driving method of the present invention, and FIG. 1 (b) is the same driving CM of the present invention.
FIG. 2 is a diagram showing a configuration example of an OS configuration output inverter, FIG. 2 is a drive pulse waveform diagram in another embodiment of the drive method of the present invention,
3 and 4 are diagrams showing examples of circuit blocks for driving an actual display panel, and FIG. 5 is a diagram for explaining the configuration of an AC-refresh type plasma display. 1,2 …… Load MOS transistor, 3 …… Output terminal, 4 ……
Diode, 5 ... Driving MOS transistor, V _H1 ...... High voltage power supply, V _H2 ...... Low voltage power supply.

Claims (2)

[Claims] 1. An XY dot matrix type in which a high voltage pulse train is applied from the scan electrode side and a low voltage pulse train of opposite phase is applied from the data electrode side, and the intersections thereof are selectively line-sequentially emitted to display information. In a method of driving an AC-refresh plasma display device, at the initial stage of applying a voltage pulse train, the total voltage value of the scanning electrode side pulse and the data electrode side pulse is sufficiently larger than the gas discharge starting voltage. A method for driving a display device, comprising applying at least one pulse, and then reducing the data electrode side pulse voltage to a level at which the total voltage value can secure a gas discharge holding voltage. 2. An XY for displaying information by applying a high-voltage pulse train from the scanning electrode side and a low-voltage pulse train of opposite phase from the data electrode side and selectively emitting line-sequential light emission at the intersections thereof.
An output inverter for driving a dot matrix type AC-refresh plasma display device, comprising one driving MOS transistor and at least two load MOS transistors having different conductivity types from the MOS transistor. Connect the load MOS transistors to power supplies of different potentials and independent gate input means, and insert a diode element at least between the load MOS transistors other than the load MOS transistor connected to the power supply with the highest potential and the output terminal. An output inverter for driving a display device, which is capable of outputting at least two kinds of different voltage pulses.